Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$234.83	4.264%	$244.8432	$244.84	$244.85	$244.80
Purchase #2	$60.97	13.606%	$69.2656	$69.27	$69.25	$69.30
Purchase #3	$60.40	12.516%	$67.9597	$67.96	$67.95	$68.00
Purchase #4	$9.33	10.671%	$10.3256	$10.33	$10.35	$10.30
Purchase #5	$35.40	10.369%	$39.0706	$39.07	$39.05	$39.10
Purchase #6	$106.50	4.874%	$111.6908	$111.69	$111.70	$111.70
Purchase #7	$168.38	10.410%	$185.9084	$185.91	$185.90	$185.90
7 purchase totals =	$675.81		$729.0639	$729.07	$729.05	$729.10